As you are selling the units at a huge markup (350GH/s cost $7,000 or less and you are selling them between $52,000 and $35,000), you will pay old investors with new investors money in order to suck more money into your scheme until it collapses. There is no legitimate business that give investors a 500% return in one year, apart from PONZI SCHEMES -> that's what you are going to run.
Anybody believing otherwise is a fool.
Actually it almost certainly is NOT a ponzi.
Nowhere do they promise to pay out 500% - that's just the fairy-tale projection they make. They can pay out what they actually promise (output of X hashes) and still pocket a load of cash - no need to be paying from future investments.
Of course their projections are total bullshit - investors will be lucky if they ever even get back what they invested. But that doesn't actually make it a scam - as that's true of nearly all mining companies (just not to such a great extent). Where it probably IS a scam is because they give projections which are totally implausible - but try convincing Trading Standards of that if you make a complaint.
Ponzi - No.
Profitable - No.
Scam - Depends on how you define it. Of course they COULD just run and pay out nothing - but that makes little sense, at least until sales dry up.